Yep. Even I've noticed this problem. Sometimes it switches the AM/PM. I've stopped using the Web interface for iCal when it comes to entering new data. I don't think there is any fix for this other than from Apple themselves.

I am in Japan currently and have been for a few weeks... I have noticed that when iCal syncs all my data is one day behind... I'm not sure if the time zones have something to do with it or not... its so much of a problem that I had to stop using it totally... I didn't notice this problem before I left the states.